The invention relates to helmets equipped with optical means of display, for example helmets used by military aircraft pilots.
Such a helmet includes a shell providing protection against perforation. This shell is lined internally with material to protect the head of the pilot against shocks; it also includes a display device. The purpose of such display devices is to present information to the pilot in symbolic form. This information is superimposed visually on the exterior landscape. When the information represents objects that are masked or not yet in sight in the landscape they must be displayed in their true direction relative to a ground-based frame of reference. For this reason and for reasons of sharpness of the image, the various parts of the display device must have fixed positions relative to each other and to the eye of the pilot.
In known helmets the display device includes means of projection of the symbolic image. The projection is carried out on a combiner that returns a reflected image towards the eye of the pilot. The projection/reflection device provides a collimated image for reasons of visual comfort. The combiner is a partially mirrored surface that transmits light rays from the exterior landscape and reflects (at least partially) light from the projection means. Generally the combiner is constituted by part of the protective visor fitted to the helmet.
The positioning of the optronic display equipment relative to the pilot's eye is carried out during a personalization phase which includes an adaptation of the liner to ensure that the future wearer of the helmet will see the symbolic image in a comfortable position.
It is known that the shell of the helmet to which the optronic display equipment is attached can be deformed by forces to which it is subjected. It is known that, in some cases, the optronic display equipment is mounted on removable structures that can be attached to fastening systems mounted on the helmet. One such arrangement is described in the U.S. Pat. No. 4,156,292, dated 29 May 1979.